Association between Chronic Ankle Instability and Autonomic Nervous System Dysfunction: A Cross-Sectional Study Compliant with STROBE Guidelines

Objective: To determine the associations between ankle instability, breathing metrics, and autonomic symptoms in adults with chronic ankle instability (CAI).Design: Cross-sectional study compliant with the STROBE statement.Methods: Fifty-five adults with CAI were recruited.CAI was defined as a Cumberland ankle instability tool (CAIT) score £25.Outcome measures included CAIT score, weight bearing lunge test (WBLT), Y-balance test (YBT), body oxygen level test (BOLT), self-evaluation of breathing questionnaire (SEBQ), Nijmegen questionnaire (NQ), heart rate variability (HRV; including heart rate [HR], standard deviation of normal-to-normal intervals [SDNN], and root mean square of successive differences [RMSSD]), and composite autonomic symptom score-31 (COMPASS-31).Pearson's correlation coefficients were calculated and simple/multiple linear regression analyses were performed using SPSS (Version 25.0;IBM Corp., Armonk, NY, USA), with a significance level set at α=0.05.Results: Worse ankle instability (lower CAIT score) was associated with lower BOLT (r=0.373),higher SEBQ (r=-0.507),and higher NQ (r=-0.356).The corresponding regressions yielded, BOLT=8.173+0.416xCAIT,SEBQ=24.213-0.658xCAIT,and NQ=17.456-0.514xCAIT.CAIT was also related to autonomic symptoms; COMPASS-31=23.806-0.690xCAIT.Respiratory-related variables significantly contributed to autonomic dysfunction; COMPASS-31=2.269+0.456xSEBQ+0.398xNQ.SDNN was correlated with HR (-) and RMSSD (+), but not with the other variables.Conclusions: In adults with CAI, greater ankle instability is associated with impaired breathing control and increased burden of autonomic symptoms.These findings suggest a potential link between mechanical ankle instability and autonomic imbalance in which diaphragmatic dysfunction may be an important factor.Future studies are required to determine whether the incorporation of diaphragm-focused breathing interventions are beneficial for autonomic stabilization and functional recovery in individuals with CAI.